1. Technical Field
The present invention relates generally to an improved data processing system, and in particular to a method and apparatus for processing data. Still more particularly, the invention relates to mechanisms for managing the restart interface in a lookahead processor.
2. Description of Related Art
In a processor that implements load lookahead instruction processing, instructions that miss the translation cache or the data cache are held for redispatch until a restart signal is activated. This mechanism is augmented by using a restart coming signal, which informs the restart mechanism that a restart signal will be forthcoming. Under normal operation, when the appropriate storage interface response is received, the restart signals are driven by either the translation cache control macros or the data cache control macros. The decision to use the translation cache control macros or the data cache control macros depends upon where a miss occurred during the processing of an instruction. Using the translation cache control macros and data cache control macros to manage misses minimizes the impact of a miss, because the missing instruction may be redispatched at the earliest possible cycle in which the miss can be resolved.
However, the rules governing the interface between the load-store unit and the instruction dispatch unit are complex. Errors could arise in the form of soft errors or in the form of unforeseen timing interactions with the memory subsystem. Any errors that take place on the interface have the potential to cause the data processing system to hang. Thus, it is desirable to have a mechanism in place to remedy any errors that occur.